Shortly after their discovery, carbon nanotubes began to appear to be a physical wonder. There were metallic and semiconductor forms; They were small and incredibly light; And they could be broken only by breaking chemical bonds. The ideas for using them seemed endless.
But then the reality of working with him came to the fore. It was difficult to obtain pure populations of the metallic or semiconductor forms. Synthesis techniques mostly produce a tangle of small nanotubes; Those that extend more than a few centimeters remain rare. And while the metal version offered little resistance to carrying electrical current, it was harder to send that many electrons down the nanotube.
However, materials scientists are a stubborn group, and they are still trying to get them to work. Today’s issue of Science includes a paper that describes adding a chemical to carbon nanotube bundles to increase their ability to carry current close to copper levels. Although the more conductive nanotubes were not stable, this discovery may point to something with a longer shelf life.
doped nanotube
Carbon nanotubes come in various forms. In the case of single-walled nanotubes, you can think of them as taking a sheet of graphene, rolling it into a circle, and joining the two opposite ends together that you just brought together. These can also be of different diameters. There are also multi-walled carbon nanotubes, where a second nanotube (and perhaps a third, and perhaps even more than that) is wrapped around the first.
When metallic, these offer little resistance to electron flow along the nanotube. But, because most of their electrons are bound in the chemical bonds required to form nanotubes, there are not many of them available to flow. Therefore, many people have tried to develop dopants – chemicals that can be added in small amounts that alter the behavior of the bulk material. In this case, the goal was to find chemicals that would act as electron donors, potentially increasing the amount of current sent down the nanotube.
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